The way we did it is that we had a starter base where we maxed out bronze age, then killed the second boss on another island (had a temporary camp there with beds, and a portal nearby), then noticed there is a massive swamp nearby the boss point, connected to a patch of meadows with a draugr camp with watchtowers and ocean access, so it was a perfect base location. We moved some bronze and copper there with the ship and and turned it into a lovely homestead. It is still our main base. After we mined out all the iron from 6-7 crypts, moved to another swamp with boat, built a smelter and forge base there with portal and didn't need to carry any iron back. We had to mine out two mountains (one near main base, one across ocean, we used the longship to haul silver back). On the 4th boss's mountain we made a mountain base underground with smelter and forge. On the next biome we are in the process of setting up another industrial base but out pretty main base is still the same as before, connected to the others with 6-8 active portals.